Obvious cruelty getting upvotes is the worst feeling. It is Lord of the Flies writ large. It is people cheering on a beating.
If it makes you feel any better I learned at Stack that people tend to downvote cruelty strongly. So what is missing in Disqus for this specific case is a downvote ability.
(I do not generally support downvoting in social discussion as it gets used for disagree far too often – and opinions cannot be objectively wrong – but I could see a lot of people downvoting this post as cruelty, which it is.)
I suppose you could flag it, but this gets into the uncertain grey areas of flagging… more realistically, this post should have been removed by a moderator.